The control of bleeding during surgery accounts for a major portion of the time involved in an operation. In particular, bleeding that occurs when tissue is incised or severed can obscure the surgeon's vision, prolong the operation, and adversely effect the precision of cutting. Blood loss from surgical cutting may require blood infusion, thereby increasing the risk of harm to the patient.
Hemostatic surgical techniques are known for reducing the bleeding from incised tissue prior to, during, and subsequent to incision. One such technique uses a heating element to transfer heat to the severed tissue to thermally reform collagen. Heat transferred from the instrument to the tissue produces a thin collagenous film which seals over the severed blood vessels and capillaries, thus reducing bleeding. Localized application of heat reduces tissue necrosis or damage that may retard healing.
Electrosurgical techniques that pass a high frequency or radio frequency current through the patient's tissue between two electrodes for both cutting and causing hemostasis tissue also are known. The current passing through the tissue causes joulean (ohmic) heating of the tissue as a function of the current density and the resistance of the tissue through which the current passes. Such heating denatures the tissue proteins to form a coagulum that seals the bleeding sites.
Monopolar electrosurgical devices employ a small electrode at the end of a handle in the surgeon's hand and a large electrode plate beneath and in contact with the patient. Only one of the two electrodes required to complete the electrical circuit is manipulated by the surgeon and placed on or near the tissue being operated on. The other electrode is the large plate beneath the patient. The electrosurgery power supply impresses high frequency voltage spikes of thousands of volts between these two electrodes, sufficient to cause an electric arcing from the small operating electrode the surgeon holds to the most proximate tissues, then through the patient to the large electrode plate beneath the patient. In the patient, the electrical current becomes converted to heat; hottest in the tissues immediately below the small hand-held electrode where the currents are most concentrated.
A principal disadvantage of monopolar electrocautery is that current flows completely through the patient. These high voltage electrical currents may arc from the small electrode to nearby non-targeted vital structures, or follow erratic paths as they flow through the patient's body, thus causing damage to tissues both near and at some distance from the electrode.
Another drawback of monopolar electrosurgical devices is the excessive tissue damage caused by the high voltage arc, including carbonization of the tissue, which compromises wound healing. Furthermore, monopolar devices typically create vision obscuring smoke, which must be evacuated from the surgical site.
In bipolar electrosurgical devices, two electrodes are closely spaced together and have the same surface area in contact with the tissue. The current flow is thus locally confined to the tissue that is disposed between and electrically connects the electrodes.
One difficulty encountered with prior art electrosurgical devices is that of controlling the current flow through the patient's tissue to obtain hemostasis in localized areas, without also heating and causing undesirable trauma to adjacent tissue. Although the introduction of bipolar electrosurgical devices has helped to localize current flow, previously known bipolar electrosurgical devices present difficulties in selectively applying the current flow.
For example, Hildebrandt et al. U.S. Pat. No. 3,651,811 and Soviet Union Patent Certificate 575,103 describe bipolar electrosurgical scissors having opposing cutting blades forming active electrodes. These devices enable a surgeon to sequentially coagulate the blood vessels contained in the tissue and then mechanically sever the tissue with the scissor blades. However, these devices apparently require the surgeon to cycle the power supplied to the electrodes during separate steps of obtaining hemostasis in the tissue and then cutting the tissue. In particular, these previously known devices require the surgeon to first energize the electrodes and grasp the tissue to cause hemostasis. Once the blood vessels contained within the tissue are coagulated, the electrodes are deenergized so that the scissor blades may be closed completely to sever the tissue mechanically. The scissors are then repositioned for another cut, and the power supply to the scissors cycled on and off again to congeal the tissue. Neither of these devices appear to permit the surgeon to maintain the electrodes in a continuously energized state, because the power supply would be shorted out or damaged if the blades were permitted to contact each other while energized.
Accordingly, a major drawback of previously known hemostatic bipolar electrosurgical cutting devices is that they have neither recognized the existence of, nor resolved the problem of, selectively delivering a current to obtain hemostasis at one location in the tissue, while simultaneously allowing already hemostatically heated tissue to be severed. It would therefore be desirable to provide a bipolar electrosurgical instrument that automatically and continuously adjusts the current delivery location so that it precedes the cutting point, without shorting the electrodes and interrupting the current providing hemostasis of the tissue.
Another drawback of previously known bipolar electrosurgical devices is the tendency for coagulum to build up on the electrode surfaces. Such buildup may impede the cutting ability of the device, cause sticking of the tissue to the device, and interfere with the surgeon's ability to manipulate the device at the surgical site.
Another related drawback is the tendency in previously known bipolar electrosurgical devices to experience some current leakage near the electrodes, which mat result in coagulum buildup on the non-active surfaces of the electrosurgical instrument as well.
It would therefore be desirable to provide an electrosurgical instrument wherein coagulum buildup on the surfaces of the instrument is reduced, thereby improving maneuverability of the instrument at the surgical site and reducing trauma to adjacent tissue.
Heretofore, no bipolar electrosurgical instrument for cutting and causing hemostasis of planar tissue areas has recognized or overcome the aforementioned problems. A continuing need for improved hemostatic electrosurgical scissors-like devices for simultaneously causing hemostasis in tissue and severing that tissue therefore exists.